We have developed two new methods for determining the shape and nature of the sensitivity profiles of spatial frequency channels (tuning curve). The first method relies on simultaneous masking of one grating by another of a different frequency. The second method uses the standard adaptation technique, but includes as a variable adapting modulation, allowing the computation of an "action spectrum" which represents channel sensitivity as the "threshold for effect" for gratings of different frequencies. Both methods avoid the theoretical objections that have plagued much of the earlier work. The results demonstrate that channels are extremely narrow. We intend to replicate these results with better psychophysical methods (forced-choice, using the staircase method). We have already implemented the paradigm on our microcomputer and have started collecting data. One question to be answered is whether the shape of a channel's sensitivity profile is a function of its peak frequency. Another involves the degree of individual variation with respect to the action spectrum. We intend to improve the theoretical tools for analyzing such data, applying Quick's formula and notions on probability and signal detection.